Electrolytic device



De@ 29, 1936. J. l., L oTscH ELECTRLYTIC DEVICE Filed Feb. l5, `1935 2 Sheets-Sheet l lINT R.

Dec. 29, 1936.

2 Sheets-Sheet 2 Filed Feb. 15, 19:55

`Patented Dec. 29, 1936 UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to improvements'in electrolytic devices, such as electrolytic condensers, rectifiers or the like, comprising film-forming electrodes. One of the principal uses of these condensers is to eliminate the alternating current ripples from rectified currents. The theory and the function of these electrolytic condensers is Well known and it will therefore be sufficient to briefly name the principal elements which most 10 of these condensers according to the standard practice comprise. Only the anode is required to be of film-forming metal, usually aluminum, but sometimes tantalum or magnesium, which when placed in a suitable electrolyte, upon application of the proper voltage, is covered -with a lm of unidirectional conductivity. The cathode,

o which, as a rule, also forms the container of the condenser, can be made of a non-oxidizable metal',

like copper or nickel, or can even be made likewise of aluminum, either bare or chromiumplated, to prevent film-forming.

'Ihe electrolyte, which entirely covers the, active part of the anode, can be of various composition, partly governed by the type of metal of which the anode is made; tantalum requiring an acid electrolyte, while the majority of aluminum condensers are provided with a borax solution. In all,caseshowever, there occurs, as a result of the electrolytic action, a continuous more or less copious formation and discharge of gas bubbles,

mostly of oxygen, and besides a great amount of heat is evolved as the chemical changes taking place are preeminently exothermic.

For the gases formed an outlet must of course be provided, but it is also important that overheating of the condenser, either in part or as a whole should be avoided. If the outer container. is made of a. good heat conductor, like copper or aluminum, it helps to disperse the heat developed, and for this reason metallic containers` serving-as cathodes, are preferable to such electrolytic condensers which are built into a nonconductive (bakelite) shell.

Furthermore, however, a free circulation of the electrolytic liquid, forming eddy currents which are as little obstructed as possible, so that they can carry the gas bubbles' formed quickly to the surface from which they can be discharged promptly to the outer atmosphere, is of the greatest importance, as these gases carry with them a great amountof the heat developed and the easier the electrolyte is thus deaerized, the lower the temperature of the condenser is kept, and

the more eflicient and dependable the active service of the whole device `m11 be found to be.

` ciently great.

And herein lies, broadly speaking, the general purpose of the improvements of electrolytic condensers, shown in mypresent invention: it is, to

. express it shortly, a free-gassing electrolytic condenser", and its various features serve this unitaryand above explained end, i. e., to aim at a. free and unhampered circulation of the electrolytic liquid and, hand in hand therewith, a prompt discharge of its gaseous components.

I am well aware that many and sundry de- 10 vices have been tried out with this and kindred objects in view, and to a certain extent have proved successful, but partly they are expensive or they attain the desired effect only to a limited degree or in a one-sided way or they are not fool- 15 proof. It was therefore my aim to combine the f best features and'merits of the present art in^a novel and unique Way which at the same time will prove less expensive, while not only reliable and foolproof but also more eflcient. l, 20

I am aware that for instance anodes have been employed, composed of a strip of sheet metal fastened to and wound spirally around a middle rod of the same metal, the turns suitably spaced apart from each other. In order to facilitate circulation of the electrolyte, the sheet metal was perforated by a multiplicity of holes.

Gas vents of various description have been devised in the tops of the containers, either in the form of holes drilled through the lid (mostly 30 consisting of insulating material) and temporar-ily plugged with wax to prevent spilling of the electrolyte during shipment. This wax plug had to be removed, when the condenser was put into service. Sometimes the vent aperture was 35 covered by a sheet of rubber which had to be punctured before 'service commenced. Or a special rubber nipple was provided in the top cover which had a slit, ordinarily closed, but supposed to open when the gas pressure was sufli- 40 But rubber, especially when in contact with metal, easily deteriorates, and if the electric installations are dismantled or the condensers are taken out, the vent apertures, now

permanently open, easily spill the electrolytic 45 It is therefore among the objects of the pres ent invention to provide a novel form of an anode `in an electrolytic condenser which permits unhampered circulation of the electrolyte solution.

A further object of my invention is to make such anode from an easily operable form of material.

Another object of my invention is to manufac-l ture such anode at a low manufacturing cost and without any waste of material. This is especially valuable when a more expensive metal like tantalum is employed.

Another object of my invention is to give the anode such form that gas bubbles easily detach themselves from it and can rise to the surface unobstructedly.

A further object of my invention is to provide a degassing or venting device which is not located in the top cover.

A further object of my invention is to provide such a venting device which is securely closed during shipment and can be relied upon to be in operative condition when installed.

Another object of my invention is to control or even eliminate the human factor from operation, i. e. to make the device foolproof.

A further object of my invention is to provide a venting device which while being closed during shipment, will be in operative condition when installed and will automatically open during service, even if personal attention is not given to it.

A further object. of my inventionis to provide a venting device of the described kind which Ain addition may be easily closed again, if desired, after automatic opening.

A further object of my invention is to provide a venting device of the kind described which, when Open, provides an ample exit for a sudden excess of gas pressure.

Other more specific objects and advantages of my device will appear as the nature of the improvements is better understood, the invention consisting substantially in the novel arrangement and correlation of instrumentalities herein fully described and illustrated in the accompanying drawings wherein similar reference characters are used to describe corresponding parts throughout the several views and4 then finally pointed out and specifically defined and indicated in the appended claims.

The disclosure made the basis of exemplifying the present inventive concept suggests a practical embodiment thereof, but the invention is not to be restricted to the exact details of this disclosure, and the latter therefore is to be understood from an illustrative, rather than a restrictive standpoint. l

In the accompanying drawings- Fig. l is a top view of a condenser in which one form of my invention is embodied;

Fig. 2 is a cross-sectional elevation, along line 2 2 of Figs. 1 and 4;

Fig. 3 is an outside view of the top end of the condenser showing the vent hole with its location index; f

Fig. 4 is a horizontal crosssection along the line 4-4 of Fig. 2;

Fig. 5 is a horizontal cross section along line 5-5 of Fig. 2;

Fig. 6 illustrates theway the anode terminal is fastened to the anode sheet;

Fig. 7 shows a modified form of a condenser and venting device in a fractional elevation, partly broken away. This modification is foolproof and automatic in operation;

Fig. 8 is a top plan, partly sectional of the modified venting device, illustrated in Fig. 7;

Fig. 9 is a detail view, showing in horizontal cross section, the venting device of Fig. 7;

Fig. 10 indicates fdiagrammatically a. slotted metal strip from which the expanded metal is manufactured of which the anodes are made;

Fig. l1 shows a further manufacturing step, the uneven expanding of the metal strip and its general outline.

Referring more in detail to the different views, numeral indicates the anode element. Instead of using a plain sheet and perforating it, as hitherto was the practice, I have found that a special lacing which in structural engineering is known as expanded metal offers several distinct advantages, not inherent in any other forms in which the anodes of electrolytic devices have hitherto been made. Expanded metal is manufactured from a metal sheet or strip which is first slotted or split in a regular methodical way by a multiplicity of cuts without any waste or discard of material. Then this partly divided and still coherent sheet is expanded to any desired degree and-within limits-into different shapes, the apertures in the sheet increasing in proportion to the tensional stresses employed.

Figures 10 and 11 illustrate this process. Fig. l0 shows the most common form of slotting the metal sheetwhich in this instance is of aluminum or other film-forming material-by rows of rectilinear slits 20s, alternately staggered. 1f a strip or sheet, thus slotted, is evenly expanded in a direction perpendicular to the slits, the lattice work formed will be uniform, and by rolling such expanded sheet together in a spiral form, an anode element can be formed which is similar in general arrangement and function to many spirally-wound and perforated anodes according to former methods, except that no cutout waste material is discarded and that the anode is made from a blank form, smaller than its finished outline indicates. However, it is also possible to expand the metal unevenly, either between suitably controlled clamping jaws or over a conical mandrel, so that the stretching force gradually increases across the sheet from one longitudinal margin 20h, perpendicular to the slots, to the other 20a. Then the strip will be expanded in an arcuate form or annular segment, as Fig. 1l indicatesan'd when this is spirally rolled together, it will form substantially an inverted conical frustum, instead of a cylindrical roll. Fig. 2 shows such a conically rolled electrode in diametral cross section.

Aside from the many perforations which afford free circulation to the electrolytic liquid it has the added advantage that any gas bubble which always forms on the surface of the electrodefrom the moment it detaches has a practically unimpeded path towards the surface and the air space above it.

Other varieties of expandedgmetal shapes, known to the trade, may be adwantageously employed in a similar manner, and my invention is therefore not confined to the pattern shown and described. The-characteristic feature is that the apertured sheets are manufactured from plain blank forms withoutany waste of material, secondly that a stretching of the blank sheet, to a greater total area either as a whole or in part takes place and that the expanded` metal sheet is made from film forming material.

As is apparent from a contemplation of an inverted hollow conical frustum, placed within a cylindrical container, there would be a waste space inside the top part as well as outside the bottom part of the frustum. To partly fill this out and utilize` it, the extreme ends of the helically wound sheet may be not cut off at right angles to the lateral margins, but at a slant. The slots 20;, if so desired, are not cut their full length where they meet this inclined parting line, but stop short of it, so as to leave the margin intact. Then the tapered oi end of the sheet can extend into the waste space in proportion as itgets larger, as may be surmised froml the end, marked 20c in Fig. 2. Fig. 4 likewise indicates the tapering oi of the sheet ends.. Two rubber bands 2|, with light contraction only, are placed around the spirally wound electrode sheet to keep it from unfolding and also to prevent direct contact with the container.

Figs. 4 and 6 indicate how they anode terminal is fastened tothe inner and lower end of the sheet. This terminal end 22 may'be formed in different ways but its main part is here shown as a slightly conical plug, 22a, threaded at the lower end22b, and insulated from the contracted neck 23A of the cylindrical container 23 by the insulating sleeve 24. The conical plug 22a is provided at its largest diameterwith a circular ilange 22 f, and above said flange it has the cylindrical neckpiece 22d which is diametrically slotted at 22g to insert the endl corner 'of the electrode sheet therein. As this sheet does not meet the terminal post in a radial direction but only approaches it tangentially, a trapezoid corner portion 20g (Figs. tand 6) is nicked in, as at 20d, bent olf in a radial inward direction and soldered into or otherwise securely fastened inthe slot of the neckpieceZZd.-

In the embodiment of the inventive principle,

as illustrated in Fig. 2, it is assumed that the l diierent turns ofi the helically-wound anode could very conveniently be, bent inwardly and bev lquiring any' cutting.

that the directrix or describing line of the sheet are converging toward the bottom end of' the condenser; it would, however, be entirely within the claimed scope vof the inventive thought, if theseturns were inclined'in the opposite direction,` so that the Whole helically wound roll would not form substantially an 'inverted conical frustum but one standing on its broad basis. With the sheets apertured and expanded, as they are, it should be apparent that the effect of facilitating the vertical ascent of the gas bubbles would be about the same and the inner end.

of the spiral which would then form an. acute angle, instead of an obtuse one, where it approaches the neck piece 22d of` the terminal,

secured within the diametal slot 22g without re- 'I'he essential feature is tate which collects at the bottom from mixing again-with the clear liquid and also prevents the formation of sediment bridges between the anode terminal and the outer container whereby a short circuit or at least a current leak might be established. v

The terminal end ofthe condenser is generally supported by a non-conducting platform 26 which as a rule carries also other devices of the electrical assembly. The contracted neck 23A, which surrounds the sleeve 24 and the anode terminal 22, passes through a metal bushing 21, consisting of a tubular shank portion, threaded on the outside and tapped .into the platform 26 and a. cushion-like flange or pad 21a on which the container bottom is seated. Between this 24 covers it, forming a secure insulation between the container and the extending end ofthe anode terminal 22. a nut 3|, threaded on the latter, securely locks the terminal, the bushing 21 and the sleeve 24 in place.

It remains to describe the venting or degassing means.

A cup-shaped cylindrical cap 32 is screwed upon the threaded top end of the container 23, but the inside of the cap is not threaded all the way up, as about half the depth of the cap from the outer rim is finished smooth, so that it closely fits uponthe periphery of the unthreaded con-l tainer wall, as indicated at 32a. A number of vent holes 34, for example two Y or three, equally distributed around the periphery of the cap, are drilled in direct alignment through. both the cap side and the container wall; consequently at a certain position which is indicated by two oppositely placed arrows, as at 33, Fig. 3, the outer and inner vent holes communicate with eachother and permit free exit to any accumulated gases, while at any other position the inner vent exits are closed by the cap. A compressible pad or gasket 35 of rubber or bre, inserted into the top of the cap, against which the upper container rim is pressed, when the cap is screwed down, provides an additional hermetic seal.

Thus the condenser may be shipped with the vent holes closed, so that no liquid is spilled, and when the condenser is installed a short unloosening turn of the cap, until the arrow points at the cap rim coincide, opens up all the vent holes `and permits the free exit of gases. f Explicit directions printed or stamped upon the lid of the condenser, similar to the legend shown in Fig.' 1, cannot fail to attract the attention of the user.

Themodication of the venting device, shown in Figs. 78 and 9, however, dispenses even with the possible chance, that a purchaser might overlook this notice or neglect to follow directions. This modified form of a condenser may be shipped with closed vent ducts radially aligned, and without any danger of being broken by a gas explosion in actual service. The essential diierence in the vent construction is the feature,

shown best inyFig. 9. A circular recess 31, of larger diameter than the vent hole in the container wall,v is countersunk to about half the thicknessl of the latter, a little disk of `-thin tinfoil 38 is inserted into this recess so as to cover the vent hole, and thereupon is placed alittle cushion or eyelet 39 of rubber or leather, so that when the cap is placed or screwed down over the container end, the tinfoil disk is firmly pressed against the vent hole. The film of tinfoil must be very thin so that any considerable gas pres sure, developing within the container, will rupture it, before becoming excessive. Thereafter of course the vent holes are permanently open; however, if one desires to dismantle the assembly and store the condensers or pack them for shipment, the ventholes can easily be closed again by simply turning the cap atrifle to the left or right so that the vents are no longer aligned. (See Fig. 9.)

The caps with this modification of the venting device may be screwed upon the container in the same way as shown in Fig. 2, or, omitting the threads between the cap and the container rim, they can be secured thereon by one or more bayonet joints, as Fig. 7 indicates. A pin 40 is tapped into the container wall and forms a locking guide for the bayonet slot 4| in the cap flange. The horizontal run of the slot should be extended far enough to allow a closing displacement of the outer vent holes in relation to the inner holes without unlocking the bayonet joint. In addition to the pad or gasket 42, corresponding to the one marked 35 in Fig. 2, there is provided a short spiral spring 43 of one to two turns with slight pitch in an ascending direction, to impart tension to the bayonet joint or joints, as can easily be understood from a contemplation of Fig. 7.

A suitable legend and arrow marks underneath the vent holes may be displayed, if desired.

It is thus seen that all the different objects listed are obtained in a very simple, inexpensive and effective way. l

In accordance with the provisions of the patent statutes, I have described my invention, but I desire it understood that it is not confined to the particular form shown and described, the same being merely illustrative, and that the invention may be carried out in other ways without departing from the spirit of my invention, and therefore, I claim broadly the right toiemploy all equivalent instrumentalities coming within the scope of the appended claims, and by means of which, objects of my invention are attained and new results accomplished, as it is obvious that the particular embodiments herein shown and described are only some of many that can be employed to attain these objects and accomplish these results.

The term expanded metal as used in the annexed claims refers to sheet metal made by a particular process .which is defined in Handbook Encyclopedia of VEngineering (The Industrial Press, 1928) page 409, as follows:

The term expanded metal is applied to sheet metal which has been stretched or expanded to form a screen, by iirst splitting the solid sheet intermittently so that the entire sheet has a series of closely spaced parallel cuts, to expand it laterally to form an open screen work. Thus rollers and diverging guides, extending the edges in a direction at right angles to the slits are employed, shortening the overall-width at the same time and by which true expanded metal, such as in building trades or for this particular invention is manufactured, and it is expressly understood that so-called expanded metal which is manufactured by employing punches or presses which extrude or stretch the fibers of the metal themselves are to be excluded from the definition, as also are all punched or perforated plates.

Having now described my invention, what I claim and desire to secure by Letters Patent, is:

1. A free-gassing electrolytic condenser, cornprising a. metallic container, adapted to serve as cathode, a fluid electrolyte and a. film-forming anode, consisting of expanded metal having open and `unobstructed slits, serving as gaspassages.

2. In an electrolytic free-gassing condenser a film-forming anode in the shape of a metal grating, spirally surrounding a free central duct in such manner that the complete roll forms a conical frustum, each helical turn being inclined at the same angle toward the mathematical axis of said frustum.

3. In an electrolytic free-gassing condenser an anode, consisting of a film-forming expanded metal sheet, spirally surrounding a free central duct in such manner that the complete roll resembles a conical frustum, each helical turn being inclined at the same angle toward the mathematical axis of said frustum.

4. In an electrolytic condenser an anode, consisting of a film-forming expanded metal sheet in the shape of an oblong parallelogram with oblique end sides, and being unevenly expanded, so as to form an arcuate segment, said segment spirally surrounding a void conical free space, thus forming a roll, substantially in the form of a conical frustum.

5. In a free-gassing electrolytic condenser, an anode made of expanded' metal having open and unobstructed slits, serving as gas passages.

6. A free-gassing electrolytic condenser, comprising a non-filming metallic container, adapted to serve as cathode, cylindrical in form with its lower end contracted into a narrow neck, an

anode terminal plug, insulatingly wedged intosaid neck and with a short shouldered stub protruding into the container and leaving the central space above it unobstructed for free gassing and the circulation of the electrolyte, a sediment retainer in the form of a non-conductive sieve, clamped between the stub shoulder and the insulation of the container neck, said sieve contacting the cathode and covering the entire space between the anode terminal plug and the cathode wall, and a' film-forming anode, made of expanded metal in the form of a spirally wound roll, forming in its entirety approximately a conical frustum, having an empty core and iixedly secured upon said protruding stub, and having its spiral turns more closely spaced at one end than at the other. v

7. In a free-gassing electrolytic condenser an anode of a standard-made expanded metal sheet in the form of a helical coil, the spiral turns of the sheet being more closely spaced at one end than at the other, so that the whole coil approximately resembles a conical frustum.

JOHN L. LOTSCH. 

